Electro-hydraulic valve positioner

ABSTRACT

The current invention relates to motor valves and actuators associated with such motor valves. More particularly, the current invention relates to an electro-hydraulic positioner for such actuators so that the valve can be opened, closed or partially opened. The invention also relates to a method for positioning an actuator for a motor valve. The method utilizes a hydraulic liquid.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/651,965 filed May 25, 2012.

FIELD OF THE INVENTION

The current invention relates to motor valves and actuators associated with such motor valves. More particularly, the current invention relates to positioning such actuators so that the valve is open, closed or partially opened.

BACKGROUND OF THE INVENTION

Motor valves are designed for use in liquid and gas control applications such as oil and water dump valves and such as burner valves. Generally, they have a valve for controlling the flow of the liquid or gas and an actuator, which controls the opening and closing of the valve based on the external input. Often the actuator has been pneumatically controlled; this involves the use of a compressed gas to position the actuator. Use of compressed gas is problematic in that a compressed gas source must be available. In field application this requires either maintaining such a compressed gas source or using locally available sources, such as gas extracted from a well. Among other difficulties, maintaining a compressed gas source is labor intensive and requires constant monitoring. Using locally available sources typically means using hydrocarbon gas; hence, there is a loss of valuable hydrocarbon gas to the atmosphere and concerns over hydrocarbon gas emissions. Additionally, the sour, wet or dirty nature of the supply gas can adversely affect the operation of the motor valve assembly and can add additional maintenance costs because of the necessity of using accessory equipment such as regulators, filters and drip pots.

Accordingly, it would be desirable to have a low maintenance system for positioning the actuator, which eliminates many or all of the concerns of pneumatic systems.

SUMMARY OF THE INVENTION

In accordance with one embodiment of the invention there is provided an electro-hydraulic valve positioner comprising a first conduit, a second conduit, a pump, a check valve and an electromechanical valve. The pump has an inlet for receiving a hydraulic liquid from the first conduit and an outlet for discharging the hydraulic liquid to the second conduit. The check valve is in fluid flow communication with the outlet of the pump and the second conduit. The check valve prevents backflow from the second conduit to the first conduit. The electromechanical valve is in fluid flow communication with the first conduit and the second conduit. The electromechanical valve has a first position allowing fluid flow between the first conduit and the second conduit, and a second position preventing fluid flow between the first conduit and the second conduit.

In accordance with another embodiment of the invention there is provided a process for positioning an actuator for a motor valve comprising:

-   -   (a) receiving a first signal regarding a state of a first fluid;     -   (b) activating a pump in response to the first signal to thus         introduce a hydraulic liquid into a second zone at a second         pressure from a first zone at a first pressure wherein the         second pressure is greater than the first pressure to thus         produce a pressure difference;     -   (c) positioning the actuator in response to the pressure         difference;     -   (d) deactivating the pump in response to a second signal wherein         the deactivating occurs when the second pressure reaches a         predetermined pressure set point;     -   (e) activating a valve in response to a third signal regarding         the state of the first fluid to thus introduce the hydraulic         liquid into the first zone from the second zone such that the         pressure difference is reduced; and     -   (f) positioning the actuator in response to the thus reduced         pressure difference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a motor valve assembly incorporating one embodiment of the current invention.

FIGS. 2A and 2B are cross-sectional views with a schematic flow diagram of the electro-hydraulic valve positioner in accordance with the embodiment of FIG. 1. FIG. 2A illustrates the flow to the second side of the diaphragm. FIG. 2B illustrates the flow from the second side of the diaphragm.

FIG. 3 is an end view of the mechanical chamber of an electro-hydraulic valve positioner in accordance with the invention.

FIG. 4 is an end view of the electronics chamber of an electro-hydraulic valve positioner in accordance with the current invention.

FIG. 5 is a cross-sectional view of an electro-hydraulic valve positioner taken along line 5-5 of FIG. 3.

FIG. 6 is an enlargement of the check valve used in an electro-hydraulic valve positioner of FIG. 5.

FIG. 7 is a partial cross-sectional view and partial schematic view illustrating an embodiment of the invention using a positional sensor.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

The current invention is directed to an electro-hydraulic valve positioner and a process for using the same. Generally, the inventive electro-hydraulic valve positioner can be used as part of a motor valve assembly, which includes a motor valve and the electro-hydraulic valve positioner; hence, the invention also is directed to an inventive motor valve assembly and a process for using the same. The electro-hydraulic valve positioner is sometimes referred to as an actuator. In general terms, actuators are a mechanism for controlling or moving another mechanism. The inventive electro-hydraulic valve positioner is described in relation to controlling a motor valve and, thus, electro-hydraulic valve positioner is an actuator in that it moves or controls the top works of a motor valve. However, the top works move or control the valve portion of the motor works and, thus, are also an actuator. To avoid confusion the term “actuator” will only be used herein in relation to describing the top works of the motor valve.

FIG. 1 shows motor valve assembly 10, which comprises motor valve 20, electro-hydraulic valve positioner 22 and fluid reservoir 24. Motor valve 20 has a top portion 26, commonly referred to as a top works 26 and a control valve 28. Top portion 26 has diaphragm housing 27 and actuator 30, which includes actuator stem 33.

Referring to FIGS. 2A and 2B, a motor valve 20 is shown in cross-section and the electro-hydraulic valve is shown schematically. Motor valve 20 is of the type having a control valve 28 and a top portion 26, which includes an actuator 30 and top portion 26. Actuator 30 is movable with a diaphragm 32 within top portion 26. Motor valves are well known in the art, and the interaction of the actuator and diaphragm are well known. The actuator 30 is connected at a first end to valve plug 70 and at a second end to a diaphragm plate 34. Diaphragm plate 34 is connected around its outer circumference to diaphragm 32. Diaphragm 32 is sandwiched around its outer circumference between upper portion 54 and lower portion 56 of diaphragm housing 27. Thus, diaphragm 32 divides the interior portion of diaphragm housing 27 into a first zone 58 on first side 60 of diaphragm 32 and a second zone 62 on second side 64 of diaphragm 32. First zone 58 and second zone 62 are sealed from fluid flow contact across the interior of diaphragm housing 27; thus, when fluid pressure is increased in one of the zones there is a pressure differential between them, the diaphragm will move towards the lower pressure zone. Spring 52 is operationally connected to diaphragm plate 34 to provide for a bias for diaphragm 32. As illustrated in FIGS. 2 and 3, motor valve 20 is in a pressure-to-open configuration. Accordingly, when pressure causes diaphragm 32 to move upwardly, the actuator 30, including actuator stem 33, will move upwardly and will open the control valve 28. In the pressure-to-open configuration, spring 52 provides a downward bias for diaphragm 32. Thus, to move diaphragm 32 upward, the pressure in second zone 62 must be greater than the pressure in first zone 58 by a predetermined amount. Generally, the predetermined amount is greater than the amount overcome the bias provided by spring 52. It is understood that for a pressure-to-close configuration, control valve 28 is normally open and pressure will be applied to the top of the diaphragm 32 to close the control valve 28 by moving diaphragm 32 downwardly and, hence, actuator 30 downwardly. In pressure-to-close configuration, spring 52 provides an upward bias for diaphragm 32. Thus, to move diaphragm 32 downward, the pressure in first zone 58 must be greater than the pressure in second zone 62 by the predetermined amount.

Control valve 28 comprises a valve housing 72, which defines a first flow channel 74, a second flow channel 76 and a valve seat 78. First flow channel 74 and second flow channel 76 are in fluid flow contact across valve seat 78; however, when valve plug 70 is sealing engaged with valve seat 78, first flow channel 74 and second flow channel 76 are prevented from fluid flow communication across valve seat 78. Accordingly, when actuator 30 is in its lower most position, valve plug 70 sealing engages valve seat 78 and there is not fluid flow communication between first flow channel 74 and second flow channel 76. As actuator 30 moves upwardly, fluid flow communication is established with maximum fluid flow when actuator 30 is in its uppermost position.

Returning now to FIG. 1, it can be seen that electro-hydraulic valve positioner 22 is in fluid flow communication with diaphragm housing by first flow line or first conduit 44 and by second flow line or second conduit 46. Additionally, first conduit 44 is in fluid flow communication with hydraulic liquid reservoir 24. As shown, the motor valve 20 is configured for pressure-to-open operation and first conduit 44 is connected to upper portion 54 at port 66 and second conduit 46 is connected to lower portion 56 at port 68. Generally, these connections will be switched for pressure-to-close configurations. During operation, diaphragm housing 27 will generally be filled with hydraulic fluid. Hydraulic liquid reservoir 24 can be any suitable container for storing additional hydraulic fluid as necessary for providing suitable hydraulic pressure to diaphragm 32. As illustrated, hydraulic liquid reservoir 24 has transparent or translucent side wall 25 so that the amount of hydraulic liquid in the reservoir can be visually inspected. The hydraulic liquid can be any suitable liquid such as water or hydraulic oil. One type of suitable hydraulic oil is hydro-treated naphthalene oils.

Turning now to FIGS. 3, 4, 5 and 6 the components of electro-hydraulic valve positioner 22 can be seen. Electro-hydraulic valve positioner 22 has valve positioner housing 42 defining an electrical chamber 41 and a mechanical chamber 43. Electrical chamber 41 contains electronic control unit or circuit board 36. Mechanical chamber 43 contains pump 40, pressure transducer 48, check valve 50 and electromechanical valve 51. Electrical chamber 41 and mechanical chamber 43 are isolated so that (other than connections for circuit board 36 to control the mechanical components), there is no contact between the chambers. As can best be seen from FIGS. 2A and 2B, pump 40 has an inlet 80 in fluid flow communication with first conduit 44 so that it receives hydraulic liquid from first conduit 44. Pump 40 has an outlet 82 for discharging the hydraulic liquid, which is at a higher pressure upon discharge than upon introduction to pump 40. Outlet 82 is in fluid flow communication with check valve 50 and second conduit 46. Check valve 50 is disposed so as to prevent backflow from said second conduit into outlet 82 and thus, back into first conduit 44. Electromechanical valve 51 is in fluid flow communication with first conduit 44 and second conduit 46. Electromechanical valve 51 has a first position, which prevents fluid flow between first conduit 44 and second conduit 46, and a second position, which allows fluid flow between first conduit 44 and second conduit 46. A sensor is utilized to control the positioning of actuator 30, such as pressure transducer 48, which senses the pressure downstream from pump 40. As illustrated in FIG. 2A and 2B, pressure transducer 48 senses the pressure on second zone 62. Alternatively or in addition to pressure transducer 48, a positional sensor 84 can be mounted as illustrated in FIG. 7 to determine the position of actuator stem 33, as further described below.

Pump 40 can be any suitable pump that can be electronically controlled, as such pumps are known in the art. Electromechanical valve 51 can be any suitable valve, such as a solenoid valve. Pressure transducer 48 can be any suitable such pressure transducer or sensors as are known in the art.

In operation, motor valve assembly 10 may be used, for example, in connection with a fluid-containing vessel to drain fluid therefrom. A liquid level controller such as, for example, an electronic liquid level controller may be connected to the fluid-containing vessel. When the fluid in the vessel reaches a level at which fluid needs to be drained therefrom, a signal will be sent to an electronic control unit or printed circuit board 36. Operation of motor valve assembly 10 can best be seen from FIGS. 2A and 2B, which include a schematic flow diagram portion for electro-hydraulic valve positioner 22.

Pump 40 contained in the valve positioner housing 42 is activated when the signal is sent. Valve positioner housing 42 is ported so that flow lines 44 and 46 are connected to ports in the valve positioner housing 42. The ports are communicated with the inlet and outlet of pump 40.

Pump 40 is activated and will operate to circulate fluid from liquid reservoir 24 through line 44 and out through line 46 into the space below diaphragm 32, that is second zone 62. The diaphragm housing 27 of top works 26 will generally be full of hydraulic fluid, but until pump 40 is activated no pressure will be acting upward on diaphragm 32. When the pressure in second zone 62 exceeds the pressure in first zone 58 by a predetermined amount, diaphragm 32 will lift actuator 30 to open control valve 28. A pressure transducer 48 will sense the pressure and will shut pump 40 off when a previously determined pressure set point is reached. A check valve 50 prevents backflow and holds the diaphragm 32 in place thus holding the valve 28 open. When sufficient fluid has been drained from the fluid-containing vessel, a signal is sent to the circuit board to open the solenoid valve 51. The solenoid valve 51 will open to allow flow therethrough back into the space above the diaphragm 32 in top works 26; that is, first zone 58. A spring 52 will urge diaphragm plate 34 downwardly to push fluid outwardly through solenoid valve 50, so that actuator 30 moves valve 28 to the closed position. FIGS. 2 and 3 are flow diagrams showing the direction of flow to open and close valve 28.

While the description here is to a discrete, or on/off version in which the actuator moves between fully open and fully closed positions, a positional sensor, which will monitor the positions of the actuator, can be used and the actuator can be moved to desired positions that correspond to the desired position of the valve between fully open and fully closed. Position feedback may be accomplished as follows.

An analog or digital signal is sent from an outside source to the printed circuit board 36 to indicate the desired position of the actuator 30 and actuator stem 33. The position of actuator 30 and actuator stem 33 is determined through a positional sensor 84, which is operationally connected to actuator 30 and actuator stem 33. Positional sensor 84 can be a rotary sensor, resistive potentiometer, hall-effect sensor or any other sensor capable of detecting the position of actuator stem 33. As shown in FIG. 7, positional sensor 84 is a rotational sensor that interacts with actuator stem 33 through means of grooves 86 and 88. For a pressure-to-open valve, the electronic control unit 36 sends a signal to operate pump 40 to circulate fluid from liquid reservoir 24 through line 44 and out through line 46 into the space below diaphragm 32 to open the motor valve 20 to the desired position. Desired position feedback is accomplished through a signal from the sensor to the printed circuit board 36. Once the desired position is reached, electronic control unit 36 sends a signal to stop pump 40. Subsequently, if motor valve 20 needs to be further opened, a signal can be sent to start pump 40 again. Alternatively, if motor valve 20 needs to allow less flow or be closed, electronic control unit 36 sends a signal to operate electromechanical valve 51 to circulate fluid from the space below diaphragm 32 through line 46 and out through line 44 into liquid reservoir 24 to close the motor valve 20 at the desired position. Desired position feedback is accomplished through a signal from the sensor to the printed circuit board 36.

Other embodiments of the current invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. Thus, the foregoing specification is considered merely exemplary of the current invention with the true scope thereof being defined by the following claims. 

What is claimed is:
 1. An apparatus comprising: an electro-hydraulic valve positioner comprising: a first conduit; a second conduit; a pump having an inlet for receiving a hydraulic liquid from said first conduit and an outlet for discharging said hydraulic liquid to said second conduit; a check valve in fluid flow communication with said outlet and said second conduit, said check valve prevents backflow from said second conduit to said second conduit; an electromechanical valve in fluid flow communication with said first conduit and said second conduit and having a first position allowing fluid flow between said first conduit and said second conduit and a second position preventing fluid flow between said first conduit and said second conduit.
 2. The apparatus of claim 1 further comprising an electronic control unit which turns said pump on in response to a first signal, turns said pump off in response to a second signal and switches said electro-mechanical valve from said first position to said second position in response to a third signal.
 3. The apparatus of claim 1 wherein said electromechanical valve is a solenoid valve.
 4. The apparatus of claim 1 further comprising a source of hydraulic liquid in fluid flow communication with said first conduit and wherein said hydraulic fluid is a hydraulic oil.
 5. The apparatus of claim 1 further comprising a motor valve operationally connected to said electro-hydraulic valve positioner such that said motor valve is changed from a first position to a second position based on flow of hydraulic liquid between said first conduit and said second conduit.
 6. The apparatus of claim 5 wherein said motor valve comprises: a control valve; and an actuator assembly having a diaphragm having a first side at a first pressure and a second side at a second pressure wherein, when said second pressure is not greater than said first pressure by a predetermined amount, said control valve is in said first position and, when said second pressure is greater than said first pressure by said predetermined amount, said control valve is in said second position; wherein said first conduit is in fluid flow communication with said first side of said diaphragm and said second conduit is in fluid flow communication with said second side of said diaphragm; and wherein said hydraulic liquid is discharged at a higher pressure than it is received, such that hydraulic liquid discharged from said pump increases said second pressure and fluid flow through said electromechanical valve decreases said second pressure.
 7. The apparatus of claim 6 further comprising an electronic control unit which turns said pump on in response to a first signal, turns said pump off in response to a second signal and switches said electromechanical valve from said first position to said second position in response to a third signal.
 8. The apparatus of claim 7 further comprising a sensor which sends said second signal to said electronic control unit when a predetermined pressure set point is reached by said second pressure.
 9. The apparatus of claim 8 wherein said sensor is a pressure transducer which is operationally connected to said actuator assembly such that said pressure transducer can sense said second pressure and send said second signal to said electronic control unit when a predetermined pressure set point is reached by said second pressure.
 10. The apparatus of claim 8 wherein said actuator assembly has an actuator stem operationally connected to said control valve and which is moved based on said second pressure and wherein said sensor is a position sensor operationally connected to said actuator stem wherein said position sensor sends said second signal when said actuator stem reaches a predetermined position.
 11. An apparatus comprising: a motor valve comprising a control valve; and an actuator assembly having a diaphragm having a first side at a first pressure and a second side at a second pressure wherein, when said second pressure is not greater than said first pressure by a predetermined amount, said control valve is in a first position and, when said second pressure is greater than said first pressure by a predetermined amount, said control valve is in a second position; a fluid reservoir for containing a hydraulic liquid; an electro-hydraulic valve positioner comprising: a first conduit in fluid flow communication with said first side of said diaphragm and in fluid flow communication with said fluid reservoir; a second conduit in fluid flow communication with said second side of said diaphragm; a pump having an inlet for receiving said hydraulic liquid from said first conduit and an outlet for discharging said hydraulic liquid to said second conduit, wherein said fluid is discharged at a higher pressure than it is received; a check valve in fluid flow communication with said outlet and said second conduit, said check valve prevents backflow from said second conduit to said second conduit; a solenoid valve in fluid flow communication with said first conduit and said second conduit and having a first position preventing fluid flow between said first conduit and said second conduit and a second position allowing fluid flow between said first conduit and said second conduit; an electronic control unit which turns said pump on in response to a first signal, turns said pump off in response to a second signal and switches said solenoid valve from said first position to said second position in response to a third signal; a sensor which sends said second signal to said electronic control unit when a predetermined pressure set point is reached by said second pressure.
 12. A process for positioning an actuator for a motor valve comprising: (a) receiving a first signal regarding a state of a first fluid; (b) activating a pump in response to said first signal to thus introduce a hydraulic liquid into a second zone at a second pressure from a first zone at a first pressure wherein said second pressure is greater than said first pressure to thus produce a pressure difference; (c) positioning said actuator in response to said pressure difference; (d) deactivating said pump in response to a second signal wherein said deactivating occurs when said second pressure reaches a predetermined pressure set point; (e) activating a valve in response to a third signal regarding said state of said first fluid to thus introduce said hydraulic liquid into said first zone from said second zone such that said pressure difference is reduced; and (f) positioning said actuator in response to said thus reduced pressure difference.
 13. The process of claim 12 wherein said predetermined pressure set point is determined based upon said first signal.
 14. The process of claim 13 further comprising generating said second signal based on the position of said actuator.
 15. The process of claim 12 wherein said first zone is on a first side of a diaphragm and said second zone is on a second side of a diaphragm and steps (c) and (f) of positioning said actuator further comprise moving said diaphragm by said pressure difference and positioning an actuating stem in response to said movement of said diaphragm.
 16. The process of claim 15 further comprising generating said second signal based on the position of said actuator stem.
 17. The process of claim 15 comprising sensing said second pressure by a pressure transducer and generating said second signal by said pressure transducer.
 18. The process of claim 12 wherein an electronic control unit receives said first signal, said second signal and said third signal, and controls said pump and said valve based on said signals.
 19. The process of claim 12 wherein said state of said first fluid is the level of said first fluid in a container. 